This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
The present invention relates generally to electrical power generation and, in an embodiment described herein, more particularly provides a downhole power generator that converts heat energy into a voltage potential usable for, inter alia, powering electronics and charging devices such as capacitors. The present disclosure is directed generally to the generation of power downhole to support higher power demands experienced during modern wellbore drilling.
Modern hydrocarbon drilling and production operations can often require that electrical power be supplied to equipment in the downhole environment. For example, electrical power is required downhole for a number of applications, including well logging and telemetry. Well logging of the borehole often includes the use of active sensors that require power to obtain information about the downhole environment. Such information will typically include the various characteristics and parameters of the earth formations traversed by the borehole, data relating to the size and configuration of the borehole itself, pressures and temperatures of ambient downhole fluids, and other vital downhole parameters. Telemetry commonly utilizes electrical power to relay data acquired from various logging sensors in the downhole environment to the surface. As technology advances with newer and better tools, the power demanded by the tools increases in order to keep the tools running in the wellbore for long periods of time.
One conventional approach to downhole electrical power generation includes circulating drilling mud to operate a generator or turbine located downhole. At least one problem with this approach is that mud flow rates can vary widely and the mud flow may need to be increased, for example when the drill bit enters a new type of subterranean strata. As the flow rate becomes excessively high, significant issues can be encountered. First, at high flow rates, the increased rotational rate produces high torques within the generator that can lead to its mechanical failure. Second, at high flow rates, more power can be generated than is necessary for the intended application. This excess power generation can lead to heat production, which can be detrimental to electronic components in the drill string. Additionally, due to the potential extreme flow rates that the circulating mud may attain, any such generator or turbine is typically oversized relative to the nominal requirement for power. The increased size of the generator or turbine leads to lower than optimal efficiency and increased cost. A conventional approach to generating a constant amount of power when the mud flow must be increased is to pull the downhole generator and reconfigure the turbine to operate at the higher mud flow rate. Pulling, modifying, and re-inserting the downhole power generator requires a significant amount of time, thereby incurring an operational cost and delaying the drilling operation.
Another conventional approach to downhole electrical power generation is simply to place more batteries in the downhole tool or tolls being operated in the wellbore. However, the addition of batteries takes up valuable space on the tool itself as well as space on the drill string. Further, batteries are flammable, explosive and dangerous and harmful to the environment.
There continues to be a need for improved electrical power sources that can be used with wellbore drilling systems.
The illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments may be implemented.